The document outlines the concept of streams in programming, originating in the 1950s, and their application in various programming languages like PHP, C, and Python. It explains key terms associated with streams such as sockets, filters, transports, and wrappers, along with their functionalities and operations. It also includes technical details on stream handling, including error handling, filtering, and user-defined filters, emphasizing the importance of understanding these concepts for effective data manipulation.

2.  Idea originating in 1950’s
 Standard way to get Input and Output
A source or sink of data
Definitions

 C – stdin, stderr, stdout
 C++ iostream
Who uses them
 Perl IO
 Python io
 Java
 C#

3. Είναι πολύ σημαντικό να
κατανοήσουμε τους  Stream
 Socket
όρους ότι το εγχειρίδιο
χρησιμοποιεί για να
εξηγήσει πώς PHP κάνει
ρέματα.  Filter
And NOT in Greek:
It is very important to
understand the terms that
 Transport
the manual uses to
explain how PHP does
 Wrapper
streams.
 Context
 Scheme
 Target

4.  Stream
› Resource that exhibits a flow or sucession of
data
 Socket
› Bidirectional network stream that speaks a
protocol
 Filter
› Performs operations on data as it is read
from or written to a stream

5.  Transport
› Tells a network stream how to communicate
 Wrapper
› Tells a stream how to handle specific
protocols and encodings
 Context
› A set of parameters and options to tell a
stream (or socket or filter) how to behave

6.  Scheme
› The name of the wrapper to be used. file, http, https, ftp,
etc.
 Target
› Depends on the wrapper, filesystem uses a string path
name, ssh2 uses a PHP resource
home/bar/foo.txt
file:///home/bar/foo.txt
http://www.example.com/foo.txt
ftp://user:pass@ftp.example.com/foo.txt
php://filter/read=string.toupper|string.rot13/resource
=http://www.example.com

7.  EVERYTHING
 include/require _once
 stream functions
 file system functions
 many other extensions

8. What are and how to use
Streams, Sockets and Filters

9. Stream
Contexts
Stream Stream Stream
ALL IO
Filter Wrapper Transport

10.  Access input and output generically
 Can write and read linearly
 May or may not be seekable
 Comes in chunks of data

12.  flock
 transport and wrapper limitations
 non-existent pointers (infinite loops can
and will happen)
 error handling

13.  Performs operations on stream data
 Can be prepended or appended (even
on the fly)
 Can be attached to read or write
 When a filter is added for read and write,
two instances of the filter are created.

15.  Data has an input and output state
 When reading in chunks, you may need
to cache in between reads to make
filters useful
 Use the right tool for the job

16.  Network Stream, Network Transport,
Socket Transport
 Slightly different behavior from a file
stream
 Bi-directional data

18.  Sockets block
› stream_set_blocking
› stream_set_timeout
› stream_select
 feof means “connection_closed”?
 huge reads or writes (think 8K)
 stream_get_meta_data is READ ONLY

19.  New APIS in streams and filesystem
functions are replacements
 Extension is old and not really kept up to
date (bit rot)
 Extension is more low level
 stream_socket_server
 stream_socket_client

20.  Pipes
 STDIN, STDOUT, STDERR
 proc_open
 popen

21.  Parameters
 Options
 Modify or enhance a stream
 stream_context_set_param
 stream_context_set_option
 stream_context_create

22. Streams, Stream Transports,
and Filters all available by
default

23.  file://
 http://
 ftp://
 data://
 glob://

25.  SSL  Phar
› https:// › phar://
› ftps://  Zlib
› ssl:// › compress.zlib://
› tls:// › zlib://
 SSH  Bzip
› ssh2.shell:// › compress.bz2://
› ssh2.exec://
› ssh2.tunnel://
› ssh2.sftp://
› ssh2.scp://

29.  string filters
› string.rot13
› string.toupper
› string.tolower
› string.strip_tags

30.  convert filters
› convert.*
 base64-encode
 base64-decode
 quoted-printable-encode
 quoted-printable-decode
 dechunk
› decode remote HTTP chunked encoding
streams
 consumed
› eats data (that’s all it does)

31.  bzip.compress and bzip.compress
 convert.iconv.*
 zlib.inflate and zlib.deflate
 mcrypt.* and mdecrypt.*

32.  tcp
 udp
 unix
 udg
 SSL extension
› ssl
› sslv2
› sslv3
› tls

33.  php://stdin
 php://stdout
 php://stderr
 php://output
 php://input
 php://filter (5.0.0)
 php://memory (5.1.0)
 php://temp (5.1.0)

35. Userland Filters and Streams

36.  There are no interfaces
 Implement as though there were an
interface
 Seekable is optional
 Flushable is optional
 Directory support is optional

37.  fopen
 file_get_contents
Information
 Return true or false
 $this->context will have any context
metadata
Code

38.  fread
 fgets
 file_get_contents
Information
 etc…
 Return string data or false
 $this->context will have any context
metadata
Code

39.  fwrite
 file_put_contents
Information
 get in a string of data to deal with
 return how many bytes you wrote
Code

40.  feof
 file_get_contents
 fread
Information
 etc…
 Return true or false
 $this->context will have any context
metadata
Code

41.  fclose
 file_get_contents
Information
 Don’t return anything
 any cleanup should go here
Code

42.  fstat calls stream_stat
 EVERYTHING ELSE uses url_stat
 Good idea to do both
 Return an array of data identical to stat()

43.  stream_seek
 stream_tell
 stream_flush

44.  mkdir
 rmdir
 dir_closedir
 dir_opendir
 dir_readdir
 dir_rewinddir

45.  stream_lock
 stream_cast
 rename
 unlink

46.  Extend an internal class php_user_filter
 It’s not abstract…
 Yes that’s a horrible name
 Remember this pre-dates php 5.0
decisions

47.  onCreate
 basically a constructor
Called every time PHP needs a new filter
Information

(on every stream)
 return true or false
Code

48.  php_user_filter
› $this->filtername
› $this->params
› $this->stream

49.  onClose
 basically a destructor
Information
 no return
Code

50.  MUST return
› PSFS_PASS_ON
› PSFS_FEED_ME
Information › PSFS_ERR_FATAL
 You get buckets of data and do stuff to
them
Code

52.  $in and $out are “bucket brigades”
containing opaque “buckets” of data
 You can only touch buckets and
brigades with the stream_bucket_*
functions
 You get a bucket using
stream_bucket_make_writeable

53. Use Case land – when streams
make sense

54.  Data in s3
 Data locally during development
 Easy switch out if alternative storage is
ever desired
 Storing image files

55.  Existing Zend Framework Code
 Register the s3:// wrapper
 Use a configuration setting for the stream
to use for all images on the system

56.  Store and edit template files in a
database
 Have the snappiness of including from
disk
 Minimal Configuration

57.  db:// stream
 simple stream wrapper that looks for the
template in the db, and writes it to the
filesystem before returning the data
 The cached location is FIRST in the
include path, so if it fails, the db stream
gets hit

58.  Talk to mercurial (hg binary)
 hg communicates via command line
 continue to pipe additional commands

59.  Use proc_open to keep a pipe to the
binary going
 Pass commands through stdin pipe as
necessary
 Abstract this out to other binaries that
are used by the system

60.  Elizabeth Marie Smith auroraeosrose@gmail.com
 http://php.net/streams
 http://php.net/filesystem
 http://ciaranmcnulty.com/blog/2009/04/simplifying
-file-operations-using-php-stream-wrappers